MPMD Simple Magnetic Draft Shield

I had designed a magnetic holder that attached to a snap-on holder but decided that the design was overly complicated. Instead I designed a simple, single unit, magnetic holder that holds a piece of cardboard over the MPMD opening. 3 clips can be used to cover all the openings. I used a piece of cardboad that is about 3mm thick. I have included a 1, 2, 3 and 4mm design in case you wish to try some other materials such as Corex or a thin clear plastic.
I glued in a single 12mm diameter neody